Twisting paper

ABSTRACT

A twisting paper substrate to be waxed for the production of an opaque waxed paper wrapping, wherein the paper substrate includes a fibrous base, at least one opacifying additive and at least one binder reducing penetration of wax in the fibrous base during the production of the waxed paper substrate by application of wax on the paper substrate, wherein the difference of opacity of the paper substrate before and after Cobb test according to the rizinus Cobb method on one side to be waxed of the paper substrate is most preferably less than or equal to 8 percent.

The present invention relates to paper wrapping applications.

The invention relates more particularly to paper used for wrapping individual food products such as pieces of candy.

Such paper is usually referred to as twisting paper and must be able to withstand the twisting involved in the high speed wrapping operation without tearing.

It must also show stable twist retention and protect the freshness of the candy while at the same time not allow the candy to stick to the inside of the paper. For this reason, the paper is waxed.

U.S. Pat. No. 3,865,664 discloses an example of a twisting paper.

U.S. Pat. No. 4,842,187 discloses an opaque biaxially drawn oriented thermoplastic film.

Opacity is one of the most important property in paper wrapping applications such as confectionery. Opaque wrapping enables to hide the wrapped product.

Opacifying additives are added in the paper to achieve high levels of opacity of the paper wrapping.

Application FR 2 685 704 A1 describes the use of TiO₂ particles as opacifying additive.

However, opacifying additives add significant costs.

Hence, there is a need to decrease the amount of opacifying additives added in twisting paper while maintaining their other required properties and the opacity of the paper wrapping or to benefit from a higher opacity at equal opacifying additive contents.

The present invention provides a twisting paper substrate to be waxed for the production of an opaque waxed paper wrapping, wherein the paper substrate comprises a fibrous base, at least one opacifying additive and at least one binder notably reducing penetration of wax in the fibrous base during the production of the waxed paper substrate by application of wax on the paper substrate, notably wherein the difference of opacity of the paper substrate before and after Cobb test according to the rizinus Cobb method on one side to be waxed of the paper substrate is most preferably less than or equal to 8 percent.

This difference of opacity may notably be less than or equal to 5 percent.

The binder leads to a decrease of wax penetration in the fibrous base during the production of the waxed paper substrate by application of wax on the paper substrate. Thus, less wax is needed, which leads to an increase of the opacity of the waxed paper substrate. Less opacifying additive is added in the paper substrate to achieve a given level of opacity of the waxed paper substrate, which reduces costs. Additional cost reduction is achieved thanks to the reduction of the wax amount. Furthermore, the reduction of the wax amount may make it easier to claim paper compostability and the waxed paper may be considered as mono-material thus decreasing the green dot fees. In addition, the wax reduction allows a better runnability on waxing machines due to the possibility to run faster and with a more stable process.

Another aspect of the invention relates to a waxed paper wrapping, comprising the paper substrate according to the invention and a coating of wax on at least one side of the paper substrate.

A further object of the present invention is a method for producing the paper substrate according to the invention, wherein the at least one binder is applied on at least one side, preferably on both sides, of a paper web comprising the fibrous base, preferably using a metered size press.

A further object of the present invention is a method for producing a twisting paper substrate to be waxed for the production of an opaque waxed paper wrapping, wherein the paper substrate comprises a fibrous base, at least one opacifying additive and at least one binder reducing penetration of wax in the fibrous base during the production of the waxed paper substrate by application of wax on the paper substrate, wherein the binder is applied on at least one side to be waxed of a paper web comprising the fibrous base.

The present invention also provides a method for producing a waxed paper wrapping according to the invention, comprising the production of the paper substrate according to the invention and application of the wax on the paper substrate.

The present invention also provides a method for packaging food, comprising twisting around the food a waxed paper wrapping according to the invention.

Another aspect of the invention relates to a packaged food product comprising a food product and a waxed paper wrapping according to the invention, twisted around the food product.

Opacity

Opacity according to the invention is the opacity as defined in norm NF Q03-006, expressed in percent.

Barrier Property Characterization of One Side to be Waxed of the Paper Substrate

In order to characterize the barrier property of one side, which is intended to be waxed, of the paper substrate, the Cobb test according to the Rizinus Cobb method can be performed, and the opacity on this side before and after the Cobb test according to the Rizinus Cobb method can be measured, as detailed below.

Cobb Test According to the Rizinus Cobb Method

This test is adapted from the standard SCAN-P 37:77 which specifies the procedure for determining the oil absorbency of paper or board.

Castor oil is applied at ambient temperature (20° C.) on one side to be waxed of the paper substrate according to the Rizinus Cobb method, which consists of the following:

The reservoir of the absorbency testing device SFT 03t model from IGT Testing Systems is filled with castor oil. The castor oil is characterized by a density comprised between 0.95 g/cm³ and 0.97 g/cm³, a saponification value comprised between 170 and 190 and an iodine value comprised between 80.0 and 95.0.

The paper substrate is placed on the castor oil reservoir, the side of the paper substrate to be tested being orientated downward, in other words towards the oil. The reservoir is closed and maintain with a lid.

The reservoir with the paper substrate is returned manually upside down, so that the castor oil is in contact with the paper substrate.

After two minutes, the paper substrate and the castor oil reservoir are returned to their initial position: the paper substrate is on the castor oil reservoir. The lid is unblocked but kept in place to maintain the paper substrate on the reservoir. The excess of castor oil on the paper substrate is removed by pulling the paper on the edge of the reservoir.

Difference of Opacity Before and after Cobb Test According to the Rizinus Cobb Method

The opacity is measured on the paper substrate before and after the Cobb test according to the Rizinus Cobb method on one side to be waxed.

The difference of opacity of the paper substrate before and after the Cobb test according to the Rizinus Cobb method is calculated as followed:

Difference of opacity (%)=Opacity before Cobb test (%)−Opacity after Cobb test (%)

The difference of opacity of the paper substrate before and after the Cobb test according to the Rizinus Cobb method on one side to be waxed of the paper substrate is related to the barrier property of this side of the paper substrate: the lowest this difference of opacity, the strongest the barrier against wax of this side of the paper substrate.

The difference of opacity of less than or equal to 8% of the paper substrate before and after the Cobb test according to the Rizinus Cobb method on one side to be waxed may be fulfilled regardless of the side of the paper substrate chosen for the application of the castor oil.

Paper Substrate

The paper substrate may have a basis weight of less than or equal to 60 g/m², preferably less than or equal to 45 g/m², notably less than or equal to 40 g/m² following the standard NF EN ISO 536.

The paper substrate is preferably a printable paper substrate.

The paper substrate may have a surface energy higher than or equal to 25 J/m² and preferably higher than or equal to 30 J/m².

The paper substrate may be calendered.

The Bekk smoothness according to ISO 5627:1995 on one side of the paper substrate may range between 1300 s and 2500 s, or even lower than 1300 s as long as the printability is good.

Fibrous Base

The paper substrate comprises a fibrous base.

The fibrous base may have of origin wood pulp, non-wood fibers, natural pulp, synthetic fibers, semi synthetic fibers or a mix of any of them.

The paper may comprise hardwood fibres and softwood fibres, for example between 60 and 70% of softwood fibres and between 30 and 40% of hardwood fibres.

Opacifying Additive

The paper substrate comprises at least one opacifying additive.

The at least one opacifying additive may comprise a pigment, the pigment preferably having a high refractive index, in particular higher than or equal to 2.30.

The at least one opacifying additive comprise preferably TiO₂ or zinc sulfide, most preferably TiO₂.

TiO₂ may be anatase titanium dioxide or rutile titanium dioxide, preferably rutile titanium dioxide.

Binder

The paper substrate comprises at least one binder, for example only one or a mixture of different binders.

The at least one binder is preferably located near the surface of the paper substrate.

According to a first embodiment of the invention, the at least one binder is a water soluble binder.

The at least one water soluble binder may be selected from PVOH or starch, preferably from PVOH.

The paper substrate may comprise PVOH and starch

According to a second embodiment of the invention, the at least one binder is a water insoluble binder.

The at least one water insoluble binder may be selected from latex made from polymers and copolymers from several monomers, notably styrene, butadiene, acrylic esters, vinyl acetate, and acrylonitrile.

The paper substrate may comprise latex made from polymers and copolymers from several monomers, notably styrene, butadiene, acrylic esters, vinyl acetate, and acrylonitrile.

In another embodiment of the invention, the paper substrate may comprise a mixture of water soluble and water insoluble binders.

The binder(s) may be part of a surface coating composition which is applied on at least one side to be waxed, preferably on both sides to be waxed, of a paper web comprising the fibrous base, during the production of the paper substrate.

The surface coating composition may be applied on one side to be waxed of the paper web in an amount of less than or equal to 5 g/m², preferably less than or equal to 3 g/m², in dry weight.

The side to be waxed on which the surface coating composition is applied may be chosen indifferently.

The surface coating composition may be applied on both sides to be waxed of the paper web in an amount of less than or equal to 5 g/m² per side, preferably less than or equal to 3 g/m² per side, in dry weight.

The paper substrate may comprise binder(s) between 1 to 20%, preferably 1 to 10%, in dry weight relative to dry weight of paper substrate. It may represent 40 to 90% in dry weight of binder(s) in the surface coating composition containing said binder(s).

Softening Agent

The paper substrate may comprise at least one softening agent.

The one or more softening agent are useful to maintain high moisture content associated with flexibility to enhance twisting without breaks nor tears during packaging after waxing.

The at least one softening agent preferably penetrates to the core of the paper substrate.

The at least one softening agent may be selected from, but not limited to, urea, nitrate, notably sodium nitrate, a mixture of urea and sodium nitrate, or an organic plasticizer such as sorbitol, sorbitol ether, polyethylene glycol or glycerol, the at least one softening agent being preferably a mixture of urea and sodium nitrate.

The paper substrate may comprise two or more softening agents, preferably selected from urea, nitrate, notably sodium nitrate, a mixture of urea and sodium nitrate, or an organic plasticizer such as sorbitol, sorbitol ether, polyethylene glycol or glycerol.

The surface coating composition containing the binder(s) may also comprise the softening agent(s).

The paper substrate may comprise softening agent(s) in an amount between 0.2 to 15%, preferably 0.5 to 5%, in dry weight relative to dry weight of paper substrate. It may represent 10 to 50% in dry weight of softening agent(s) in the surface coating composition containing said softening agent(s).

Other Additives

The paper substrate may comprise at least one additional additive.

The at least one additional additive may be a rheology modifier, preferably a carboxymethyl cellulose.

The at least one additional additive may be an insolubilizing agent.

The paper substrate may comprise both rheology modifier and insolubilizing agent.

The surface coating composition containing the binder(s) may also comprise the other additive(s).

Addition to the Fibrous Base

The at least one binder may be applied on at least one side to be waxed, preferably on both sides to be waxed, of a paper web comprising the fibrous base, preferably using a metered size press.

The at least one binder may be applied on at least one side to be waxed, preferably on both sides to be waxed, of a paper web comprising the fibrous base, using a size press.

The at least one opacifying additive may be mixed to the fibrous base before formation of the paper web.

The at least one softening agent may be applied on at least one side to be waxed, preferably on both sides to be waxed, of the paper web, preferably using a metered size press.

The at least one softening agent may be applied on at least one side to be waxed, preferably on both sides to be waxed, of the paper web, using a size press.

The at least one softening agent and the at least one binder may be applied on at least one side to be waxed, preferably on both sides to be waxed, of the paper web at the same step or at different steps, preferably at the same step.

Although the at least one softening agent and the at least one binder may have different properties, the softening agent penetrating to the core of the paper substrate and the binder remaining near the surface of the paper substrate, it has been surprisingly found that it is possible to apply them on at least one side to be waxed, preferably on both sides to be waxed, of the paper web at the same step.

The size press or the metered size press enables in particular to apply the at least one binder and/or the at least one softening agent on one or both sides to be waxed of the paper web at high speed.

Twisting Paper Substrate

The paper substrate is a twisting paper substrate.

A twisting paper substrate according to the invention is a paper substrate having a cross-direction (CD) elongation according to ISO 1924 higher than or equal to 7.5%, a machine direction (MD) tear resistance according to ISO 1974 higher than or equal to 200 mN, a CD tear resistance higher than or equal to 220 mN and a stiffness according to ISO 2493 (15° 5 mm) not higher than or equal to 40 mN in the MD and not higher than or equal to 20 mN in the CD.

The twisting paper substrate according to the invention has suitable deformation and resistance capacity for absorbing torsion energy during packaging without being torn. This can be described as paper twistability.

Twisting paper substrates according to the invention are able to match compromise between barrier and twistability. Barrier properties against wax are notably brought by the at least one binder and twistability is notably brought by the at least one softening agent.

Known twisting papers can give good twistability due to high flexibility and special surface treatments but wax penetration is out of control due to broadly opened surface.

Application

The paper substrate may be used for confectionery applications, notably sweets twisting application.

Wax

The wax may be a hydrocarbon wax. It may be extracted and refined from petroleum, resulting in for example paraffin, or derived from gas synthesis, resulting in a synthetic wax.

The wax may be a vegetable wax. It may be fatty and derivated from palm oil, soy oil and rapeseed.

Waxed Paper Wrapping

The production of the waxed paper wrapping comprises the production of the paper substrate according to the invention and the application of wax on at least one side, preferably on both sides, of the paper substrate.

Therefore, the waxed paper wrapping comprises the paper substrate according to the invention and a coating of wax on at least one side of the paper substrate, preferably on both sides.

The waxed paper wrapping may consist of the paper substrate according to the invention and the coating of wax on one side or on both sides of the paper substrate.

The paper substrate may be remoistered, notably with a blend comprising water, glycerol and sorbitol, before wax application

Wax may be present on at least one side of the paper substrate, forming one layer on the application side of the paper substrate and penetrating at least partially in the fibrous base.

Wax may be present on both sides of the paper substrate, forming one layer on each side of the paper substrate and penetrating at least partially in the fibrous base.

At least one side of the paper substrate may be printed before application of wax. Thus, the waxed paper wrapping may comprise at least one printed mark on the paper substrate and under the wax layer.

The waxed paper wrapping may consist of the paper substrate according to the invention, the coating of wax on one side or on both sides of the paper substrate and one or more printed marks on the paper substrate and under the coating of wax.

The waxed paper wrapping preferably does not comprise any additional layer on the paper substrate which has the property to reinforce the barrier against wax.

Before the wax coating on one side or on both sides of the paper substrate, an additional treatment, independent of the potential printing step, can be performed to improve a property other than the barrier against wax, such as for example twistability.

The wax quantity in the fibrous base may be less than or equal to 7 g/m², preferably less than or equal to 5 g/m², preferably less than or equal to 4 g/m² when the wax is applied on both sides of the paper substrate.

The wax quantity in the fibrous base may be less than or equal to 4 g/m², preferably less than or equal to 3 g/m², better to 2.5 g/m², even better to 2.0 g/m² and even better to 1.5 g/m², when the wax is applied on one side of the paper substrate.

Such a low wax quantity enables to give relevant cost advantages, environmental advantages with easier compostability, and more stable processes.

The difference of opacity between the paper substrate, before application of wax, and the waxed paper wrapping may be less than or equal to 10%, preferably less than or equal to 5%, notably less than or equal to 3%

Opacity is measured in an unprinted area of the waxed paper wrapping.

Packaged Food Product

The packaged food product comprises a food product and a waxed paper wrapping according to the invention, twisted around the food product.

The waxed paper wrapping may be twisted in at least one turn around the food product.

The food product is preferably entirely wrapped in the waxed paper wrapping.

The food product may be a confectionery food product, such as a sweet.

EXAMPLES Paper Substrates

The fibrous base is a standard fibrous base used for confectionery application which main characteristics are presented in table 1.

TABLE 1 Fibrous base characterization Fibrous base Standard AVG SD Basisweight (g/m²) ISO 536-1995 E 40.4 0.1 Tear MD mN ISO 1974-1990 E 302 10 Tear CD mN 298 11 Stiffness MD mN ISO 2493-1: 2010 41.1 6.2 (15°-5 mm) ISO 5628-1990 E Stiffness CD mN 20.1 2.5 (15°-5 mm) Breaking length MD Km ISO 1924-2-1994 6.81 0.53 Breaking length CD Km 2.42 0.30 Elongation MD % NF EN ISO 1924-2-1994 3.7 0.1 Elongation CD % 9.6 0.7

Two different surface treatments have been tested, applied each time on both sides of the paper substrate:

-   -   A surface coating recipe according to the invention, SP-1.     -   A surface coating recipe corresponding to a standard recipe         SP-2.

Table 2 presents details of both recipes.

TABLE 2 coating recipes characterization. Recipe SP-1 SP-2 In composition of the surface Urea 30.73 79.9 layer Nitrate 5.27 13.7 (in % by dry weight) Starch * 2.46 6.4 PVOH ** 46.73 Carboxymethylcellulose*** 10.96 Insolubilizing agent **** 3.85 Solid content target (%)   8%   8% Solid content measured (%) 8.22% 8.30% Viscosity (mPa/s) 92 13 T° C. 25 23 pH 7.79 7.85 * Perfectafilm A115 from Avebe ** Celvol 325 from Sekisui Chemical Co, Ltd ***DP 100N from Lamberti **** Cartabond TSI from Archroma Managment GmbH

A size press has been used to apply the surface treatments on the fibrous bases.

The conditions were the following: 2 presses at 25 PJ hardness and 4 bars pressure in the nip. Speed was 40 m/min with oven set at 140° C.

Coatweight is about 2 g/m² total dry weight on both sides of each fibrous base.

In this way, two paper substrates have been produced, each comprising a fibrous base and a surface coating (SP-1 or SP-2).

Paper Substrates Characterization:

Table 3 presents the main paper characteristics of these two paper substrates.

Both paper substrates are twisting paper substrate according to the invention (see table 3 tear, elongation and stiffness values).

SP coating according to the invention (SP-1) can provide high barrier property to paper while SP-2 is not giving the expected barrier level (see delta opacity after rizinus cobb values of table 3)

TABLE 3 Paper substrates characteristics Fibrous base SP-1 SP-2 Standards AVG SD AVG SD Basis weight g/m² ISO 536-1995 (E) 42.42 0.21 41.41 1.09 Bekk Smoothness Front Side sec ISO 5627: 1995 2421 175 2130.17 144 Bekk Smoothness Reverse Side sec 149.00 5.79 146.20 15.45 Elongation CD % NF EN ISO 1924-2- 10.48 0.86 9.82 0.59 1994 Tear MD mN ISO 1974-1990 (E) 227.40 10.94 269.70 3.79 Tear CD mN 232.00 3.74 271.70 13.28 Stiffness (15°-5 mm) MD mN ISO 2493-1: 2010 36.20 4.08 29.60 1.71 Stiffness (15°-5 mm) CD mN 19.60 1.84 17.20 1.23 Delta opacity after Front Side % According to the 3.30 1.55 14.40 1.20 rizinus cobb specification Delta opacity after Reverse Side % According to the 3.50 1.99 13.20 0.01 rizinus cobb specification

Waxed Paper Wrappings

The paper substrates_have been remoistered with a blend Water/Glycerol/Sorbitol and waxed on both sides with paraffin wax heated at 105-110° C.

The quantity of wax that is applied ranges between 7 and 8.5 g/m² in dry weight.

Table 4 presents wax coatweights measured inside papers. SP-1 is showing a wax saving of 33% compared to SP-2.

The amount of TiO2 present in the paper substrate was the same in both cases, and equal to 3.5% of the weight of paper substrate but the difference of opacity before and after waxing is much lower with SP-1 coating, which is a different way to prove lower wax penetration thanks to wax barrier provided by SP-1 coating.

TABLE 4 Wax saving Fibrous base Standards SP-1 SP-2 Wax coatweights inside paper (g/m²) 5.05 7.55 Wax saving inside vs. SP-2 (%) 33.11% Opacity before waxing (%) NFQ 03-006 63.55 65.32 Opacity after waxing (%) NFQ 03-006 59.49 53.2 (Measured on waxed samples) Delta opacity after waxing (%) 4.06 12.12

Therefore coating SP-1 is able to provide suitable barrier to save quantity of wax applied on twisting paper substrates according to the invention.

Because of this wax saving, less opacifying additive needs to be added in the paper substrate to achieve a given level of opacity of the waxed paper wrapping, which reduces costs. 

1. A twisting paper substrate to be waxed for the production of an opaque waxed paper wrapping, wherein the paper substrate comprises a fibrous base, at least one opacifying additive and at least one binder reducing penetration of wax in the fibrous base during the production of the waxed paper substrate by application of wax on the paper substrate, wherein the difference of opacity of the paper substrate before and after the Cobb test according to the Rizinus Cobb method on one side to be waxed of the paper substrate is less than or equal to 8 percent.
 2. The paper substrate according to claim 1, wherein said difference of opacity is less than or equal to 5 percent.
 3. The paper substrate according to claim 1, wherein said difference of opacity is fulfilled regardless of the side of the paper substrate chosen for the application of the castor oil.
 4. The paper substrate according to claim 1, wherein the at least one opacifying additive comprises TiO₂ or zinc sulfide.
 5. The paper substrate according to claim 1, wherein the at least one binder is a water soluble binder, wherein the at least one water soluble binder is selected from PVOH or starch or a mixture of PVOH and starch.
 6. The paper substrate according to claim 1, wherein the at least one binder is a water insoluble binder, wherein the at least one water insoluble binder is selected from latex made from polymers and copolymers from several monomers.
 7. The paper substrate according to claim 1, wherein the paper substrate comprises a mixture of at least one water soluble binder, wherein the binder is selected from PVOH or starch or a mixture of PVOH and starch, and at least one water insoluble binder, wherein the binder is selected from latex made from polymers and copolymers from several monomers.
 8. The paper substrate according to claim 1, wherein the paper substrate comprises at least one softening agent, wherein the at least one softening agent is selected from urea, nitrate, a mixture of urea and sodium nitrate, or an organic plasticizer including sorbitol, sorbitol ether, polyethylene glycol or glycerol.
 9. The paper substrate according to claim 1, having a basis weight of less than or equal to 60 g/m² according to the standard ISO
 536. 10. The paper substrate according to claim 1, having a surface energy higher than or equal to 25 J/m².
 11. A waxed paper wrapping, comprising the paper substrate according to claim 1 and a coating of wax on at least one side of the paper substrate.
 12. The waxed paper wrapping according to claim 11, wherein the wax is present on at least one side of the paper substrate, the wax forming one layer on each of the application side(s) of the paper substrate and penetrating at least partially in the fibrous base.
 13. The waxed paper wrapping according to claim 11, wherein the difference of opacity between the paper substrate, before application of wax, and the waxed paper wrapping is less than or equal to 10%.
 14. A method for producing a twisting paper substrate to be waxed for the production of an opaque waxed paper wrapping as defined in claim 1, wherein the paper substrate comprises a fibrous base, at least one opacifying additive and at least one binder reducing penetration of wax in the fibrous base during the production of the waxed paper substrate by application of wax on the paper substrate, wherein the binder is applied on at least one side to be waxed of a paper web comprising the fibrous base.
 15. A method for producing the paper substrate according to claim 1, wherein the at least one binder is applied on at least one side to be waxed of a paper web comprising the fibrous base.
 16. The method according to claim 14, the binder being part of a surface coating composition which is applied on said side to be waxed of the paper web, the surface coating composition being applied on said side in an amount of less than or equal to 5 g/m² dry weight.
 17. The method according to claim 14, the at least one opacifying additive being mixed to the fibrous base before formation of the paper web.
 18. The method according to claim 14 for producing the paper substrate comprising at least one softening agent selected from urea, nitrate, a mixture of urea and sodium nitrate, or an organic plasticizer including sorbitol, sorbitol ether, polyethylene glycol or glycerol, wherein the at least one softening agent and the at least one binder are applied on at least one side to be waxed of the paper web, at the same or at different steps.
 19. A method for producing a waxed paper wrapping according to claim 11, comprising: the production of the paper substrate comprising a fibrous base, at least one opacifying additive and at least one binder reducing penetration of wax in the fibrous base during the production of the waxed paper substrate by application of wax on the paper substrate, wherein the difference of opacity of the paper substrate before and after the Cobb test according to the Rizinus Cobb method on one side to be waxed of the paper substrate is less than or equal to 8 percent; and application of the wax on the paper substrate.
 20. A method for packaging food, comprising twisting around the food a waxed paper wrapping according to claim
 11. 21. A packaged food product comprising a food product and a waxed paper wrapping according to claim 11, twisted around the food product.
 22. The packaged food product according to claim 21, wherein the food product is a confectionery food product. 